en to ko translation catalogue (3 entries)

[ctx: Month and year used in a tree above the actual days. Have a look at https://doc.qt.io/qt-5/qdate.html#toString to see which variables you can use and ask kde-i18n-doc@kde.org if you have problems understanding how to translate this]
en: MMMM yyyy
ko: yyyy년 MMMM

en: Today
ko: 오늘

en: Calendar
ko: 달력
